Many blogs provide commentary on a particular subject; others function as more personal online diaries; others function more as online brand advertising of a particular individual or company. A typical blog combines text, images, and links to other blogs, Web pages, and other media related to its topic. The ability of readers to leave comments in an interactive format is an important contribution to the popularity of many blogs. Most blogs are primarily textual, although some focus on art (art blogs), photographs (photoblogs), videos (video blogs or "vlogs"), music (MP3 blogs), and audio (podcasts). Microblogging is another type of blogging, featuring very short posts. In education, blogs can be used as instructional resources. These blogs are referred to as edublogs.
On 16 February 2011, there were over 156 million public blogs in existence. On 20 February 2014, there were around 172 million Tumblr^[4] and 75.8 million WordPress^[5] blogs in existence worldwide. According to critics and other bloggers, Blogger is the most popular blogging service used today, however Blogger does not offer public statistics.^[6][7] Technorati has 1.3 million blogs as of February 22, 2014^[8]